174 PALEONTOLOGY OF THE EUREKA DISTRICT. 
width about twice the height; beaks moderately prominent and incurved, 
situated near the anterior end, which is rather abruptly rounded; basal line 
slightly sinuate midway; posterior end obliquely rounded, truncate above 
the lower third, rounding into the basal line and forming a very obtusely 
rounded angle with the cardinal margin; cardinal line nearly straight and 
declining towards the anterior end; umbonal ridge prominent, subangular, 
becoming more rounded toward the extremity of the posterior portion of 
the shell. 
Surface showing a few lines of growth. Anterior muscular scar small, 
semicircular, and near the anterior margin; posterior scar subcircular, not 
strongly defined, situated on the postero-cardinal slope, near the margin. 
This species resembles Nyassa recta Hall (Pal. N. Y., vol. v, pt. 1, 
Plates and Explanations, p. 14, pl. liii, figs. 1-8, 1883) of the Hamilton 
Group of New York, but differs in the outline of the valves and its less 
prominent beaks. 
Formation and localities—Lower Devonian; on the west slope of 
County Peak, Middle to Upper Devonian, at Rescue Hill, west of Rescue 
Canon, Newark Mountain, and east side of Packer Basin, Eureka District, 
Nevada. 
Genus GRAMMYSIA De Verneuil. 
Grammysia minor n. sp. 
Plate xv, figs. 15, 15a. 
Shell very small, transversely elongate-ovate; valves ventricose; beaks 
strongly incurved, situated near the anterior end, which slopes abruptly 
from the beak with a slightly concave outline to the somewhat sharply 
rounded end that passes below into the basal line; this, with the exception 
of a slight sinuosity caused by the median or byssal groove, is transverse 
to where it rounds up slightly on the posterior margin to meet the oblique 
line of the upper postero-margin, with which it forms an obtuse angle, 
giving the posterior end of the shell’a pointed appearance; cardinal line 
straight about two-thirds the length of the valve; umbonal ridge rounded 
or subangular, postero-cardinal slope abrupt. 
Surface marked by rather strong, rounded concentric ridges and fur- 
rows that are nearly obsolete on the posterior umbonal slope. 
